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A fractal vise is largely a gimmick. The biggest problem we encounter with vises is the phenomenon of jaw lift. There will always be some amount of play betwee

A fractal vise is largely a gimmick. The biggest problem we encounter with vises is the phenomenon of jaw lift. There will always be some amount of play between the moveable jaws and the base of the vise, there will always be some amount of deflection, so applying clamping forces tends to force the vise jaws apart in a v-angle rather than the jaws remaining strictly parallel. This causes problems with repeatability and reduces maximum clamping force, because the clamping force is pushing the part up and out of the vise. A lot of engineering effort goes into minimising and mitigating jaw lift. A fractal vise will always be more susceptible to jaw lift, because the play between those recursive segments will add together. Each segment might only be slightly out of square when under clamping force, but that adds up to a large parallelism error at the clamping faces. The practical alternative for milling would be something like an Adaptix vise, which uses multiple sliding and locking fingers to allow the clamping faces to adapt to a non-parallel part. Other alternatives would include 3D-printed soft jaws, soft jaws molded with a low-Tg polymer like polycaprolactone, or an adhesive workholding system like Blue Photon. https://www.norgrenworkholding.com/en https://www.norgrenworkholding.com/en

blincoln 3y ago
The Adaptix vice seems like a nice approach for a lot of use cases, but unless I'm mistaken, the fractal vice seems like it will get a better grip to prevent curved objects from turning with less pressure applied from the vice, right? i.e. if someone is working with material other than metal and doesn't want to damage it? Regardless, I'm a little shocked that a) I've never seen either of these designs manufactured by low-cost brands like Harbor Freight, and b) the ones that are out there are so expensive. A complete Adaptix vice setup is $7000? I'm sure that makes sense for professional machinists or people working with a LOT of force, but surely a hobbyist version could be made for a sale price less than $100, maybe $200 for a heavy-duty version. It's basically just a big vice that has two smaller, perpendicular vices for its jaws, and the smaller vices have captive, sliding metal bars between their jaws, right? I'm pretty sure I could make a set of jaws that would suit my purposes out of parts that would cost no more than $25 at the hardware store. It would have saved me an awful lot of headache on small hobby projects over the years, so I'm probably just going to go ahead and hack one together. Either of the fractal designs (classic "teeth at the ends" version versus "flat-faced", for lack of better names) seem like they would require a decent amount of fairly precise machining, so I can understand them costing more, but $2000 for an Ali Express version still seems high.

blincoln 3y ago

The Adaptix vice seems like a nice approach for a lot of use cases, but unless I'm mistaken, the fractal vice seems like it will get a better grip to prevent curved objects from turning with less pressure applied from the vice, right? i.e. if someone is working with material other than metal and doesn't want to damage it? Regardless, I'm a little shocked that a) I've never seen either of these designs manufactured by low-cost brands like Harbor Freight, and b) the ones that are out there are so expensive. A complete Adaptix vice setup is $7000? I'm sure that makes sense for professional machinists or people working with a LOT of force, but surely a hobbyist version could be made for a sale price less than $100, maybe $200 for a heavy-duty version. It's basically just a big vice that has two smaller, perpendicular vices for its jaws, and the smaller vices have captive, sliding metal bars between their jaws, right? I'm pretty sure I could make a set of jaws that would suit my purposes out of parts that would cost no more than $25 at the hardware store. It would have saved me an awful lot of headache on small hobby projects over the years, so I'm probably just going to go ahead and hack one together. Either of the fractal designs (classic "teeth at the ends" version versus "flat-faced", for lack of better names) seem like they would require a decent amount of fairly precise machining, so I can understand them costing more, but $2000 for an Ali Express version still seems high.